Place pumpkin cubes on a sheet of baking paper in a baking tray. Sprinkle with olive oil and roast in the oven until starting to get soft and browned. (about 30 minutes at 180°)
When the pumpkin is done remove it from the oven and cut into smaller pieces.
In the meantime put water on to boil for the pasta. When it starts to boil add salt and bring to the boil again
Blend garlic, walnuts, grated orange rind and orange juice with 2 tablespoons of olive oil in a blender or food processor until quite fine.
Add the cheese and pulse 2-3 times again. If the mixture is too dry add a little more olive oil between pulses.
Add the pumpkin to the blender. Pulse 2-3 times more. You don’t want the pumpkin to be too smooth so it is better to add it last.
Stir in salt and pepper as required. The pesto is now ready
Heat a little olive oil in a medium sized frying pan.
Add the olives and cook them briefly.
Add the pesto sauce to the frying pan and mix it well with the olives.
Cook the pasta al dente in the boiling salted water according to the instructions on the packet. When the pasta is cooked, save a cup of the cooking water and strain it, add it to the pesto-olive sauce. If the sauce seens to dry, add some of the saved pasta cooking water.
Mix well and serve with a few chopped walnuts, parsley and grated parmesan.
Buon Appetito